Cyclotella paleo-ocellata, a new centric diatom (Bacillariophyta) from Lake Kinneret (Israel)

© Czech Phycological Society (2015). Large, subfossil populations of an unknown centric, planktonic diatom were observed in a lake sediment core from Lake Kinneret (Israel), which is here described as Cyclotella paleo–ocellata sp. nov. The new taxon, which belongs to the Cyclotella ocellata species complex, is described and separated from other similar taxa (e.g., Cyclotella ocellata, Cyclotella kuetzingiana, Cyclotella polymorpha, Cyclotella paraocellata) based on a combination of the following morphological characters: valve diameter, number of orbiculi depressi (circular depressions), number of striae/10 μm, stria length, number and position of rimoportulae and the number of central and marginal fultoportulae. Cyclotella paleo–ocellata can be distinguished mainly by two prominent characteristics: (1) the number and the arrangement of the orbiculi depressi (4–8) which increase with the valve diameter and (2) the marginal fultoportulae, situated on each, every second or third costa. Since Cyclotella paleo–ocellata is at present only known from the subfossil bottom sediments of Lake Kinneret, its ecological preferences are inferred simply from the associated diatom flora

Notes to the use of Aulacoseira taxa in the palaeoecological reconstruction of the Bohemian forest lakes

Aulacoseira taxa are the most abundant members of diatom assemblages in Prášilské Lake (Czech Republic) during the Holocene. These dominant diatom taxa were studied in freshwater lacustrine sediments in order to harmonize data for subsequent diatom-based palaeoecological reconstruction. Nine taxa were distinguished within the genus, six of them (A. alpigena, A. lacustris, A. laevissima, A. lirata, A. perglabra, A. valida) showed clear features for identification, the rest three taxa (A. nivalis, A. pfaffiana, A. aff. tenella) required deeper analysis. We decided to use taxa in species rank, A. nivalis (W. Smith) English et Potapova and A. pfaffiana (Reinsch) Krammer, in spite of their hardly odds and the earlier suggested merging. Morphology of A. aff. tenella was also discussed in detail. Despite all endeavours, to distinguish some specimens belonging to the A. distans species complex using light microscope is impossible and a classification into the aggregates is needed. We suggested counting the valve face views and the valve mantle views separately, in order to repair subsequent potential misidentifications more simply